This invention relates generally to communication devices for deaf, deaf-blind, or non-vocal individuals, and more particularly the invention relates to a communication system which utilizes an instrumented glove.
While many deaf persons communicate effectively using a form of sign language or the fingerspelling alphabet, problems arise when a hearing person, who does not know sign language, attempts to interact with a deaf individual who does not know the "oral" method, i.e., cannot speak intelligibly and read lips. For deaf-blind persons, communication is even more difficult since they must be able to touch the hand of the person with whom they wish to interact. These communication difficulties adversely effect interpersonal relationships and vocational activities. Consequently, many deaf, deaf-blind and non-vocal people avoid situations requiring interaction with hearing persons. These disabled individuals often remain unemployed and dependent, and cannot fully participate in community life.
The most common ways a nonvocal deaf or deaf-blind person communicates with a hearing person who does not know sign language are via interpreters and notewriting. Although interpreters are effective in translating sign language or fingerspelling into speech and vice versa, they are often expensive and difficult to acquire on a moment's notice. Use of an interpreter also leads to a loss of independence and privacy. Notewriting is used by many nonvocal individuals to communicate with someone who is seated nearby, but it is awkward while walking, standing at a distance, and when more than two persons participate in a conversation.
Several communication devices, most notably the telecommunications device for the deaf (TDD) and the Telebraille, have been developed to assist individuals with hearing or speaking disabilities. While these devices are effective for telephone conversations, neither is practical as a portable, hand-held unit which could be used for personal interaction during daily encounters at such places as a store, restaurant or bank. Thus, there is a great need for a portable communication aid which would permit deaf, deaf-blind and non-vocal individuals to engage in conversation among themselves and with hearing, vocal persons.
The use of instrumented gloves in a communication system has heretofore been proposed. See U.S. Pat. No. 4,414,537 (Grimes), U.S. Pat. No. 4,542,291 (VPL Data Glove) and Foley, "Interfaces for Advanced Computing," Scientific American, pp. 127-135, October 1987.
The VPL glove is the only commercially available instrumented glove. The Grimes glove was made strictly to recognize fingerspelling and hence has greatly limited itself as a general-purpose instrumented glove. It relies heavily on binary contact sensors to detect finger positions, and the Grimes letter recognition algorithm requires a largelookup table stored in memory. "Hard" letter decisions are made depending on which sensing contacts are made. As previously stated, by not including a full set of analog sensors to report where each finger is located, the Grimes glove and system limits itself solely to recognition of predetermined hand formations, without provisions for monitoring of customized finger positions. Also, if a hand formation is extremely close to one of the acceptable hand formations, but one finger misses its contact sensor by 0.001", the lookup table will either choose the wrong letter or will not choose any letter at all. By including analog sensors, intelligent "soft" decisions can be made, such as when a finger does not reach desired position but is sufficiently close, the appropriate letter will still be recognized.
The VLP DataGlove does remedy several of the problems associated with the Grimes glove. The VPL glove does include a full set of analog sensors which allow the user to determine analog finger positions, not just whether or not one finger is touching another in a certain location. VPL uses a modified fiber optic wire that is designed to lose light as the wire is bent, and thus attenuate the output signal. The three main drawbacks to this sensor technology are that the sensor outputs:
1. vary nonlinearly with angle of flexure, PA1 2. are dependent on the radius of curvature of the bend, PA1 3. are largely coupled to neighboring sensors.
Since the sensor is nonlinear (actually V.sub.out ae.sup.-b.theta.), when the angle of flexure is doubled the output does not double. Lookup table conversions can be used to linearize V.sub.out vs. .theta., but as .theta. becomes larger, a change in .theta. produces a much smaller change in V.sub.out. Therefore, the sensors become very insensitive for high .theta..
Since the VPL sensor is based on losing light as the optic wire is bent, sensor output is not only dependent on the overall angle of flexure, but more importantly (unfortunately) on the radius of curvature. For example, a very sharp, small angle may yield a higher output than a very rounded, large angle. This is a very undesirable trait because the sensors cannot be calibrated such that a certain voltage output corresponds to a certain angle of flexure because the output is also determined by how "sharp" is the person's knuckle.
Unfortunately, in addition, the VLP sensors are inherently omnidirectional sensors that not only produce output when bent along the desired axis but also produce unwanted output when a nearby finger is bent. When bent, a finger pulls slightly on the glove material attached to all neighboring sensors, causing erroneous lateral deflection and, hence, parasitic output signal.